[freediver]

There is no difference in terms of building something on top of Bing or Yandex as your private data never touches their servers. All they get is anonymized stream of queries, in this case from DuckDuckGo.

And yes you can compete with Google (for a certain target group) by paying them for their search results. Results are just a distribution channel, it is what you do with them that matters. For example Google and DuckDuckGo both choose to show you ads and affiliate links but that is hardly the only option.

[bad_user]

How do you know that your personal data never touches those third party servers?

Sorry, but I don't trust DuckDuckGo that much and when technology fails, I'd rather use a search engine based in a country that has rule of law ;-)